This invention relates to a housing for electronic microdevices as specified in the characterizing clause of claim 1, and to a battery cover for electronic microdevices.
One relatively frequent problem encountered these days in electronic microdevices such as hearing aids is battery corrosion in the battery compartment. Apart from the unattractive appearance of deposits that accumulate in the housing, such corrosion can progressively destroy the device. The majority of users, however, are bothered most of all by the unsightly deposits that form on the battery and in the housing. This problem becomes particularly conspicuous when such microdevices, for instance hearing aids, are subjected to a perspiration test.
There have been a variety of approaches in an attempt to bring this corrosion problem under control especially in the case of hearing aids. One such attempt has been to seal the housing as airtight as possible or to improve the situation in the device by installing a siccative. Other approaches have placed the emphasis on regular care of the device or on overcoming the problem by storing the devices in desiccating boxes. Prior art has described and documented the most diverse approaches and solutions to the problem.
Significantly, however, the use of siccatives or storage in dry chambers can only be a temporary solution since siccatives are spent after a certain time while storage in a dry place usually precludes the actual use of the device.
One objective of this invention is therefore to introduce a solution to the problem described above, i.e. a solution to the corrosion problem, that allows electronic microdevices to be used even in a moist environment while preventing for instance hearing aids from being destroyed by perspiration.
According to the invention, this objective is achieved by means of a housing as described in claim 1 and, respectively, by the use of a battery cover for electronic microdevices.
As a proposed solution, the housing for electronic microdevices especially such as hearing aids and others intended for use in an environment of elevated moisture or humidity levels incorporates at least one wall section that is perforated or porous and, facing the outside of the housing, said wall section is provided with a nonwoven fabric or fibrous pad whose pores are smaller in diameter than those of said wall section of the housing.
It is further proposed to taper the perforations or pores of the porous wall section in such fashion that the pore diameter decreases from inside the housing toward the outside.
Finally, it is proposed to additionally provide a retaining feature that holds the fibrous pad against the outside of the wall section. Alternatively, in lieu of such a holder, the fibrous pad can be attached to the wall section for instance by means of a so-called velcro strip or it may be held in place by a double-sided adhesive tape or similar means.
The wall section referred to may for instance be in the form of a housing cover serving to securely close off the electronics inside the housing or a battery compartment in that housing. In other words, said wall section may be a housing cover and in particular a battery cover. Correspondingly, in the case of hearing aids it constitutes the cover of the battery compartment.
The method per this invention, designed to prevent excessive corrosion of the battery for instance in the battery compartment of a hearing aid, utilizes the phenomenon of capillary action. In this case, what used to be a detrimental effect is turned into a positive effect. The capillary action (capillary rise) is known to vary as a function of the diameter or gap width of a capillary structure. If in one and the same material only the gap width is varied, the capillary rise is determined by the surface tension. If in any such combination the diameter and/or gap width is varied, the result will be a surface tension-dependent pressure differential that draws any fluid in the direction of the smaller diameter or gap. These considerations have led to the realization that the liquid or fluid will always move in the direction of the smaller gap. That realization in turn has spawned the underlying idea of this invention whereby the fluid, moisture or perspiration can be drawn, xe2x80x9csiphoned offxe2x80x9d as it were, into very small capillaries. Accordingly, this invention proposes to mount a fibrous pad on a perforated battery cover that serves to draw off the moisture that may enter the device for instance from a switch and to prevent any fluid from penetrating through the battery cover into the device.
One advantage of this solution over others that seal the device in airtight fashion is that it allows for xe2x80x98breathabilityxe2x80x99 i.e. ventilation which is important especially for the zinc-air batteries common today.
As a result, any moisture that may already have entered the device will dry off more rapidly and over time a quasi-dry normal state will be established.
The positive effect of a battery cover designed according to the invention has been clearly determined in a perspiration test, mentioned above, revealing a distinct difference between it and a battery compartment not equipped with a battery cover per the invention. The housing equipped as provided for by this invention had a clean battery compartment.
By way of an example the following will explain this invention in more detail, with reference to the attached drawings in which: